Mean Population Density Research Articles

Population dynamics of Myzus persicae on tobacco in Yunnan Province, China, before and after augmentative releases of Aphidius gifuensis

The population dynamics of Myzus persicae were investigated in the field in a year without releases of Aphidius gifuensis (1998–1999), in a year with A. gifuensis releases (2000–2001) and several years later (2005–2007). The results showed that both high mean population densities and damage rates did not differ between 1998 and 1999, but were significantly lower in 2000–2001 and 2005–2007. Moreover, farmers also reported the decrease of M. persicae populations and attributed the declines to augmentative releases of A. gifuensis in their own fields, indicating farmers’ recognition in the effectiveness of A. gifuensis for M. persicae control. In addition, compared with the historical data on pesticide use for M. persicae control, the number of insecticide applications and cost of M. persicae control was sustained at a low level in 2007 (several years after release of A. gifuensis). This suggests that the augmentative releases of A. gifuensis could be effective and sustainable in M. persicae control.

Impact of urban sprawl on overweight, obesity, and physical activity in Sydney, Australia.

Obesity and inadequate physical activity are major risk factors for many diseases. The built environment plays an important role in influencing participation in physical activity. We aimed to determine whether urban sprawl in Sydney, Australia is associated with overweight/obesity and levels of physical activity. We used a cross-sectional multilevel study design to relate urban sprawl (based on population density) measured at an area level to overweight/obesity and levels of physical activity measured at an individual level whilst controlling for individual and area level covariates in metropolitan Sydney. Individual level data were obtained from the 2002 and 2003 New South Wales Population Health Survey. We had information on 7,290 respondents. The mean population density was 2,168 persons per square kilometer (standard deviation=1,741, range=218-7,045). After controlling for individual and area level covariates, for an inter-quartile increase in sprawl, the odds of being overweight was 1.26 (95% CI=1.10-1.44), the odds of being obese was 1.47 (95% CI=1.24-1.75), the odds of inadequate physical activity was 1.38 (95% CI=1.21-1.57), and the odds of not spending any time walking during the past week was 1.58 (95% CI=1.28-1.93). Living in more sprawling suburbs increases the risk of overweight/obesity and inadequate physical activity despite the relatively low levels of urban sprawl in metropolitan Sydney. Modifications to the urban environment to increase physical activity may be worthwhile.

Analysis of fire events and controlling factors in eastern india using spatial scan and multivariate statistics

.Vegetation fires are one of the most serious environmental problems in several ecoregions of India. The purpose of this study is to characterize spatio‐temporal characteristics of fire events in Orissa state, eastern India. In this study, ATSR satellite remote sensing data have been used to quantify fire events from 1997 to 2006. The spatial scan statistic that quantifies ‘hotspot’ areas of fire risk has been used to identify statistically significant fire clusters during the ten‐year time period. To assess the causative factors of fires, topographic, vegetation, climatic, anthropogenic and accessibility factors were used in a robust multivariate statistical framework. Results suggested a clear variation in hotspots of fire occurrences among districts. Of the several districts, the most likely cluster of fire events has been identified in Jharsuguda district followed by secondary clusters in Gajapati, Phulbani, Anugul, Debagarh, Balangir and Raygada. The first three principal components (PCs) from multivariate statistical analysis could explain 70.48% of variance in biophysical and socio‐economic indicators of fire events. The loadings were fairly large and highly positive for deciduous forest percentage, elevation, slope mean, aspect mean, and rural population density in the first PC explaining 40.21% of variance. The second PC included drought index, average temperature and illiteracy explaining nearly 19.2% variance. The third PC had a strong positive association with cropped area and forest cover explaining 10.98% of the total variance. Overall, by quantifying the disparities in fire events in space and time, this study demonstrates the utility of the spatial scan statistic in identifying priority areas of fire risk. Our results on fire hotspots and causative factors of risk can guide forest managers toward the best management strategies for avoiding damage to forests, human life, and personal property in the study area.

Molecular Diversity of the Rumen Microbiome of Norwegian Reindeer on Natural Summer Pasture

The molecular diversity of the rumen microbiome was investigated in five semi-domesticated adult female Norwegian reindeer (Rangifer tarandus tarandus) grazing on natural summer pastures on the coast of northern Norway (71.00 degrees N, 25.30 degrees E). Mean population densities (numbers per gram wet weight) of methanogenic archaea, rumen bacteria and ciliate protozoa, estimated using quantitative real-time polymerase chain reaction (PCR), were 3.17x10(9), 5.17x10(11) and 4.02x10(7), respectively. Molecular diversity of rumen methanogens was revealed using a 16S rRNA gene library (54 clones) constructed using pooled PCR products from the whole rumen contents of the five individual reindeer. Based upon a similarity criterion of <97%, a total of 19 distinct operational taxonomic units (OTUs) were identified, nine of which are potential new species. The 16S rRNA sequences generated from the reindeer rumen exhibited a high degree of sequence similarity to methanogens affiliated with the families Methanobacteriaceae (14 OTUs) and Methanosarcinaceae (one OTU). Four of the OTUs detected belonged to a group of uncultivated archaea previously found in domestic ruminants and thought to be dominant in the rumen together with Methanobrevibacter spp. Denaturing gradient gel electrophoresis profiling of the rumen bacterial 16S rRNA gene and the protozoal 18S rRNA gene indicated a high degree of animal variation, although some bands were common to all individuals. Automated ribosomal intergenic spacer analysis (ARISA) profiling of the ruminal Neocallimastigales population indicated that the reindeer are likely to contain more than one type of anaerobic fungus. The ARISA profile from one animal was distinct from the other four. This is the first molecular investigation of the ruminal methanogenic archaea in reindeer, revealing higher numbers than expected based on methane emission data available. Also, many of the reindeer archaeal 16S rRNA gene sequences were similar to those reported in domesticated ruminants in Australia, Canada, China, New Zealand and Venezuela, supporting previous findings that there seems to be no host type or geographical effect on the methanogenic archaea community structure in ruminants.

Effects of food limitation and emigration on self-thinning in experimental minnow cohorts

Summary 1. The theory of food-regulated self-thinning (FST) for mobile animals predicts population density (N) to be an inverse function of mean body mass (W) scaled to an exponent (b), such that N = k W−b, where k is a constant. FST also predicts energy requirements (or energy flow) to remain constant over time (termed energetic equivalence) as losses to cohorts (e.g. emigration and mortality) are balanced by increased growth of surviving individuals. 2. To test these predictions, we analysed the dynamics of six experimental minnow cohorts. Replicate populations of fish were held under identical conditions with a constant and limited supply of food over a 126-day period. Half of the cohorts were open to emigration, and half were closed so that fish could only be lost through starvation mortality. 3. Patterns of self-thinning indicated non-linear changes in population density and energy flow in relation to changes in mean body mass and time, respectively. Non-linear patterns of self-thinning were probably due to a delayed growth response to changes in population density effected through mortality and/or emigration. Contrary to results of similar experiments on other fish, emigration did not have a significant influence on the pattern of self-thinning. 4. These results may be attributed to trophic interactions within cohorts and the importance of social behaviour to cohort dynamics. Both population density and energy flow in our experimental populations appeared to cycle, with episodes of starvation and mortality alternating with food recovery and weight gain, as predicted by recent models of stepwise die-off and stunted growth in animal cohorts. 5. Most of the support for FST in mobile animals comes from observational data on mean body mass and population density. Potentially important mechanisms, including the manner in which individuals are lost or retained in populations, are usually not investigated directly. Such tests of FST can only provide equivocal support. Detailed observational study and controlled experiments are needed to understand casual mechanisms.

Rainforest fragmentation and the demography of the economically important palm Oenocarpus bacaba in central Amazonia

We summarize a long-term study of the effects of edge creation on establishment of the economically important arboreal palm Oenocarpus bacaba in an experimentally fragmented landscape in central Amazonia. Recruitment and mortality of large individuals (≥10 cm diameter-at-breast-height) were recorded within 21 1-ha plots in fragmented and intact forests for periods of up to 22 years. In addition, 12 small (0.7 × 14 m) sub-plots within each 1-ha plot were used to enumerate the abundance of seedlings and saplings (5–400 cm tall). On average, the recruitment of large trees was over two times faster near forest edges, leading to a sharp (90%) increase in the mean population density of large individuals near forest edges, whereas the density of larger trees remained constant in the forest interior. Overall seedling and sapling density was significantly lower in edge than interior plots, but edge plots had a much higher proportion of larger (>100 cm tall) saplings. Our findings demonstrate that forest edges can have complex effects on tree demography and that one must consider all tree life stages in order to effectively assess their effects on plant populations.

Foraminifera and Nematoda community within the area of Ahnfeltia tobuchiensis field in Stark Strait (Peter the Great Bay of the Sea of Japan)

In August of 2006 in Stark Strait (in the Peter the Great Bay) Foraminifera and Nematoda communities were investigated at two stations: in bottom under a red alga Ahnfeltia tobuchiensis bed and on a site located outside of the bed. Bottom sediments at the stations are represented by sands of various silting extent. Foraminifera dominated at both stations, the second place by abundance was occupied by Nematoda. Extremely high population density of meiobenthos, 14278.9 ± 4623.1 thousand sp./m2, was observed under the Ahnfeltia bed. The foraminifera percentage was 98.1%, which was probably connected with the mass development of diatom algae on Ahnfeltia. A high degree of domination of one Foraminifera species was recorded—Cribroelphidium frigidum. Nematoda constituted 1.5% with the prevalence of Comesomatidae family representatives. At the station situated outside of Ahnfeltia field mean population density of meiobenthos was an order lower—1731.8 ± 621.3 thousand sp./m2. Foraminifera constituted 63.8% of the total meiobenthos density with Eggerella advena as the dominating species. Among Nematoda (12.5%) Paracanthonchus macrodon, Axonolaimus seticaudatus and Monoposthia latiannulata were dominant. Foraminifera and Nematoda community under Ahnfeltia bed, where bottom sediments are more silted, had low indices of species diversity and a high degree of domination.

Group dynamics and local population density dependence of group size in the Pyrenean chamois, Rupicapra pyrenaica

Several models have recently confirmed the hypothesis that mean group size should increase with population density in animal species in which groups are unstable. Based upon different assumptions with respect to the mechanisms of groups merging and splitting up, these models, however, predict quantitatively different relations between mean group size and population density. Taking advantage of a quasiexperimental situation, we studied the diurnal group dynamics of the Pyrenean chamois within a 58-ha open pasture in a protected area during winter. Mean group size scaled with local population density raised to the power of 2/3 within the pasture, which implies that the mean number of groups was related to the cube root of local population density. On the basis of the fate of groups that included tagged individuals, we found that: (1) the rate at which groups joined increased as the number of groups within the pasture increased; (2) the rate at which groups split up increased with their size; and (3) the rate at which groups were involved in both fusion and fission events increased as the local population density increased. We discuss the possible role of population spatial structure and mother–kid association in both the dynamics of group formation and the relations between mean group size and population density.

Efficacy of Beauveria bassiana (Bals.) Vuill. against the tarnished plant bug, Lygus lineolaris L., in strawberries

Abstract Beauveria bassiana has a high insecticidal potential to control the tarnished plant bug, Lygus lineolaris, a significant pest of strawberries. Screening experiments showed that L. lineolaris adults were susceptible to several B. bassiana isolates. Another screening test with Coleomegilla maculata, a natural enemy found in strawberries, was also performed in order to select the isolate having lower entomopathogenic impact on this insect. Based on data obtained from both insect species and on the ecozone origin of the B. bassiana isolates, INRS‐IP and INRS‐CFL isolates were selected for further experiments. The LC50 values of these two isolates against L. lineolaris adults were 7.8 × 105 and 5.3 × 105 conidia/ml, and average survival time (AST) values were 4.46 and 4.37 days at a concentration of 1 × 108 conidia/ml respectively. Results also indicated that L. lineolaris nymphs are susceptible to the selected isolates. During field experiments, using a randomized block design with four replicates, INRS‐IP and INRS‐CFL isolates were applied at two rates (1 × 1011 and 1 × 1013 conidia/ha) weekly during a period of 4 weeks. These multiple applications triggered a significant reduction of L. lineolaris nymphal populations in strawberries. Twenty‐four days after the first application, a significant difference was observed between the mean population densities of surviving nymphs in all B. bassiana‐treated plots (less than one insect per five plants) compared with those in control plots (four insects per five plants). During the field experiment, persistence of insecticidal activity and viability of B. bassiana conidia were also monitored. The results showed the presence of viable and infective conidia up to 6 days after each application on strawberry foliage. Moreover, the multiple applications of B. bassiana at the rate of 1 × 1013 conidia/ha triggered a significant reduction in strawberry fruit injuries induced by L. lineolaris feeding behaviour compared with the control plots.

Population density and seasonal activity of the threatened Madagascar spider tortoise (Pyxis arachnoides arachnoides) of the southern dry forests; South West Madagascar

The Madagascar spider tortoise Pyxis arachnoides is facing pressure from habitat destruction, hunting for food and collection for the exotic pet-trade. Very little is known of the biology and ecology of P. arachnoides. This study centres on a subspecies population of P. arachnoides arachnoides, within the southern dry forests of the Anakao region of southwest Madagascar. Surveys were carried out across 83, one hectare, quadrants over 12 months, during both the wet and dry seasons, with respective seasonal mean population densities recorded at 4.63 and 2.08 individuals per ha. This significant variation was accompanied by a variation in micro habitat preference between the seasons, with P. a. arachnoides moving to areas of greater vegetation cover during the warmer wet season. P. a. arachnoides was only recorded as feeding during the wet months, a period of increased activity. The subspecies became less active during the dry season, with some individuals entering a dormant phase. There was generally a greater abundance of females encountered throughout the year, usually weighing less than males. Juvenile abundance peaked during February and March. Six-year-old specimens were the most regularly encountered individuals and a mean age throughout the survey was recorded at 11.25 years.

Kinetics of Aggregate Formation in Social Insects

A model for the kinetics of aggregation in social insects which accounts for stochastic effects arising from individual variability and covers both the early and the mature stages of the process is developed. Different aggregation scenarios are studied, depending on the degree of cooperativity and the mean population density. It is shown that under certain conditions, the system evolves slowly to a single cluster incorporating all individuals, or to two coexisting clusters of similar sizes.

Variation in adult shell morphology and life-history traits in the land snail Oreohelix cooperi in relation to biotic and abiotic factors

ABSTRACTIn this study, we explore factors influencing variation in adult shell morphology and life-history characteristics (offspring size and number) in the ovoviviparous land snail, Oreohelix cooperi, from the Black Hills, South Dakota and Wyoming, USA. To date, no study of shell morphology and life-history characteristics in ovoviviparous land snails has included a combination of datasets including genetic data, life-history traits, shell morphology and multiple environmental factors. We report that differences in shell size among populations are strongly related to mean annual temperature (and the highly correlated variable elevation) and population density (measured as shell density). In addition, shell size varies among populations, despite an apparent lack of population genetic differentiation. Common factors thought to influence adult shell size, like precipitation and calcium levels, do not have a significant effect in this study. Adult size strongly influences per-clutch reproductive output, with larger snails having larger and more offspring. As mean annual temperature and shell density affect adult shell size, they also indirectly affect per-clutch output. The results suggest that a large portion of the life-history variation in O. cooperi is environmentally induced, as has been found in oviparous land snails and brooding freshwater bivalves.

The importance of unmanaged coastal wetlands to waterbirds at coastal Ghana

AbstractGhana's 550 km coastline has about 100 wetlands out of which five large ones are managed as Ramsar sites, the rest being unmanaged. Recent pollution and misuse of unmanaged wetlands have necessitated a study into their roles in the support of waterbirds. Waterbird survey on four wetlands between September 2005 and April 2006 revealed that 51 waterbird species make use of the managed compared to 44 in the unmanaged wetlands. Average numbers of waterbirds were higher on the managed wetlands (10,510 ± 4862) than on the unmanaged wetlands (1348 ± 602) (P &lt; 0.05) but mean population density of waterbirds (n/ha) was the same for both the managed (1860 ± 310) and unmanaged (1400 ± 220) (P &gt; 0.05) wetlands. The population densities of waterbirds belonging to guilds 1, 5 and 7 were significantly higher on the managed wetlands (P &lt; 0.05). In contrast, guilds 2 and 4 have significantly higher population densities on the unmanaged wetlands while the population density of guild 3 was the same (P &gt; 0.05). There was an indication that during mid and late periods of the nonbreeding season, the unmanaged wetlands altogether may support a larger number of waterbirds belonging to guilds 2, 3 and 4 than the five managed wetlands.

A Macroevolutionary Explanation for Energy Equivalence in the Scaling of Body Size and Population Density

Across a wide array of animal species, mean population densities decline with species body mass such that the rate of energy use of local populations is approximately independent of body size. This "energetic equivalence" is particularly evident when ecological population densities are plotted across several or more orders of magnitude in body mass and is supported by a considerable body of evidence. Nevertheless, interpretation of the data has remained controversial, largely because of the difficulty of explaining the origin and maintenance of such a size-abundance relationship in terms of purely ecological processes. Here I describe results of a simulation model suggesting that an extremely simple mechanism operating over evolutionary time can explain the major features of the empirical data. The model specifies only the size scaling of metabolism and a process where randomly chosen species evolve to take resource energy from other species. This process of energy exchange among particular species is distinct from a random walk of species abundances and creates a situation in which species populations using relatively low amounts of energy at any body size have an elevated extinction risk. Selective extinction of such species rapidly drives size-abundance allometry in faunas toward approximate energetic equivalence and maintains it there.

Production of mummichog (Fundulus heteroclitus): Response in marshes treated for common reed (Phragmites australis) removal

The invasion of U.S. east coast salt marshes by common reed (Phragmites australis) and the efforts to remove it and restore marshes to their natural vegetation (Spartina spp.) can directly impact mummichog (Fundulus heteroclitus) as this abundant species is critically linked to marsh habitat. We estimated population density, growth, and biomass to determine production of mummichog in treated Phragmites (''Treated,'' now dominated by Spartina), untreated Phragmites, and naturally occurring Spartina habitats in Delaware Bay using throw traps for small fish (mean 5 24.1 mm standard length or SL, 95% CI 5 10-38) and tag/recapture for large fish (mean 5 36.5 mm SL, 95% CI 5 18-64). Mean population density of small fish on the marsh surface was significantly higher in the Spartina (20.2 fish m 22 ) and Treated (14.1 fish m 22 ) habitats than in the Phragmites (0 fish m 22 ) habitat. Population density of large fish was similar among all three habitats (mean 5 0.9-1.7 fish m 22 ). Mean absolute growth rates of large fish were significantly higher in the Spartina (0.24 mm d 21 ) and Treated (0.24 mm d 21 ) habitats than in the Phragmites (0.13 mm d 21 ) habitat. Mean monthly mummichog production during June to September varied among habitats with Spartina highest (1.22 g dw m 22 mo 21 ), Treated intermediate (0.51 g dw m 22 mo 21 ), and Phragmites lowest (0.07 g dw m 22 mo 21 ). Small fish were the largest contributor to the production estimates in Spartina and Treated habitats. The Phragmites habitat had little or no standing water at low tide (i.e., optimal habitat for small fish was lacking), and thus, it had the lowest production for mummichog. These results also indicated that Treated marshes were more similar to Spartina than to Phragmites habitat; therefore, it appears that habitat quality and mummichog production can be increased with restoration.

Ecological factors facilitating city-dwelling in red-rumped parrots

The red-rumped parrot (Psephotus haematonotus), which appears to be undergoing range expansion, started colonising metropolitan Melbourne ~30 years ago. The factors that have facilitated this colonisation have not been evaluated. We investigated aspects of the parrot’s ecology at six parkland sites through late autumn and winter 2006 to elucidate these factors. The predominantly ground-feeding red-rumped parrot consumed mainly seeds of exotic grass and herb species, four of which were particularly important in providing a continuous winter food resource. Two of these species were common turf grasses and their visible and concealed seeds provided &gt;50% of the diet. Sites occupied by parrots had relatively more native trees, tall trees and dense canopy cover than unoccupied sites; this may be important in providing suitable daytime and nocturnal roost sites. Little aggressive interference competition occurred with other ground-feeding birds. Mean population density in occupied sites was 1.3 parrots ha–1. Mean flock size was 10 ± 6 and, on average, males comprised 67 ± 19% of a flock’s members. We suggest that abundant, continuously available food (seed) resources, apparently limited competition for food and the presence of suitable roosting sites are probably important in facilitating winter occupancy of parkland by red-rumped parrots in Melbourne.

Occurrence and Distribution of Actinomycetes in Marine Environs and their Antagonistic Activity against Bacteria that is Pathogenic to Shrimps

The mean population density of actinomycetes in water samples from eight stations off Little Andaman Island in India ranged from 0.29 x 103 CFU/ml at station 2 (Naval Area) to 0.45 x 103 CFU/ml at station 4 (Chandra Nallah). Density in sediment samples ranged from 1.21 x 103 CFU/g at station 2 (Naval area) to 3.29 x 103 CFU/g at station 6 (Buttler Bay). Forty-one strains were isolated and tested for their antagonistic activity against Vibrio alginolytics, V. harveyi, and V. parahaemolyticus, bacteria that are highly pathogenic to shrimps. Over 60% of the strains (26) exhibited varying degrees of antagonistic activity. Among them, six showed good activity and were tentatively identified as Streptomyces xantholiticus, S. aureofasciclus, S. galtieri, S. vastus, S. galbus, and S. rimosus. Results suggest that actinomycetes from the marine environment can be used as bio-control agents in shrimp culture systems to control diseases caused by bacteri- al pathogens.

POPULATION DENSITY AND HABITAT USE OF MULE DEER (ODOCOILEUS HEMIONUS) ON SANTA CATALINA ISLAND, CALIFORNIA

Abstract We conducted spotlight counts along a 41-km transect to estimate population density and habitat use of mule deer (Odocoileus hemionus), an introduced mammalian herbivore on Santa Catalina Island, California. Mean population density, calculated using distance-sampling procedures, was 5.41 deer/km2 (95% CI: 4.40, 6.65) during the 11 months of our study. Deer used island chaparral, human-developed areas, and to a lesser degree, riparian vegetation more than expected, and bare areas, grasslands, and woodlands less than expected, based on the availability of these habitats in our study area.

Postflood movements and population connectivity in gambusia (Gambusia holbrooki)

Abstract – A population of the exotic pest fishGambusia holbrookiinhabiting a drainage channel was sampled regularly to record responses to flooding and subsequent population reestablishment. The flood reduced numbers in the channel to near‐zero levels. After remaining very low for 2 months, densities increased steadily through juvenile recruitment and the concentration of fish in drying pools. Tagging revealed that in general, movements between pools separated by only a few metres were relatively limited. There was evidence for habitat segregation and population subdivision, as fish from different pools varied markedly in terms of mean population density, movement behaviour, sex and size composition and juvenile recruitment. The most favoured pool was relatively deep, well lit and had the greatest habitat diversity. Gambusia control measures are likely to be most effective if timed to coincide with floods (which reduce local population densities) and/or droughts (which concentrate fish and allow targeting of source populations).

Spatial and temporal distribution of endemic entomopathogenic nematodes in a heterogeneous vegetable production landscape

Abstract Entomopathogenic nematodes within the families Steinernematidae and Heterorhabditidae (Order: Rhabditida) are potential biological control agents for many soil-dwelling vegetable pests. However, their low persistence and efficacy after field releases have resulted in limited use in pest management programs. Understanding the factors regulating natural populations of entomopathogenic nematodes may provide insight into practices to conserve populations within production systems. A series of investigations were conducted within a vegetable production area in Willard, Ohio during 2000–2003 to gain insight into the population ecology of endemic populations of entomopathogenic nematodes. A total of 440 sites across four habitats associated with the production landscape were sampled to ascertain the natural occurrence of these beneficial nematodes. Habitats included cultivated areas, grassy banks adjacent to cultivated areas, undisturbed shrub lands and forests. Twelve sites along grassy banks were monitored over a growing season to estimate associations between abiotic and biotic factors and endemic populations. Entomopathogenic nematodes were only detected along grassy banks adjacent to the cultivated areas; nematodes were recovered from 15 to 30% of sites sampled in 2001 and 2002, respectively. Two species of nematodes were isolated, Heterorhabditis bacteriophora Poinar and Steinernema feltiae Filipjev. H. bacteriophora was the most prevalent nematode species and was recovered from 60% of positive samples. Nematode populations varied temporally and spatially along grassy banks; mean population density over the growing period was 1313 infective juveniles/m2. Neither macro- nor microarthropod communities nor soil temperature differed between sites at which nematodes were detected and those at which nematodes were not detected. Soil moisture, however, was associated with the occurrence and persistence of nematodes along grassy banks; mean soil moisture at sites at which nematodes were detected and those sites at which nematodes were not detected was 37.3 and 26.8%, respectively. Water management is an important component of vegetable production and our results suggest that soil moisture manipulation would be important in the establishment and sustained presence of entomopathogenic nematode populations within cultivated areas over the growing season.